What a New Prognostic Scoring Study Reveals About Post-Mastectomy Radiotherapy and Breast Cancer Recurrence Risk

While current breast cancer guidelines recommend reserving post-mastectomy radiotherapy (PMRT) for high-risk patients with at least four involved axillary lymph nodes (LNs), a recently published study looking at a prognostic scoring system for locoregional recurrence (LRR) suggests that PMRT may also be beneficial for those at intermediate risk of recurrence.

In the retrospective study involving 1,103 post-mastectomy patients and a median follow-up period of 11.4 years, researchers looked at the impact of PMRT on locoregional recurrence control rates (LRCs). In addition to finding a greater than 11 percent improvement in LRCs at five years with the use of PMRT in high-risk patients (96.87 percent vs. 85.71 percent without PMRT), the study authors noted a 12.5 percent improvement at five years for medium-risk patients with one to three positive axillary LNs (98.24 percent vs. 85.74 percent).

“ … We would recommend adding PRMT to the treatment of patients at intermediate and high risk of recurrence (LRR score 2 or more) because our data show significantly better 5-year LRC rates with PMRT in the intermediate-risk group versus no PMRT, as well as a tendency towards significantly better 5-year LRC in the high-risk group with PMRT versus no PMRT,” wrote Caroline Weltens, MD, PhD, a professor in radiation oncology at Katholieke Universiteit Leuven (KU Leuven) in Belgium, and colleagues.

Weltens and colleagues also found that PMRT resulted in a 13.79 percent improvement in the five-year LRC rate for intermediate-risk patients who had a greater than 2 cm tumor size and multicentricity (98.04 percent vs. 84.25 percent without PMRT).

Validating a previously established prognostic scoring system for locoregional recurrence in post-mastectomy patients, the study authors utilized four prognostic factors, including involved axillary LNs, age, estrogen receptor status and lymphovascular status, to determine LRR risk. Weltens and colleagues noted that 62.38 percent had a low LRR risk (LRR score 0-1), 30.37 percent had intermediate LRR risk (LRR score 2-3) and 7.25 percent of patients had high LRR risk (LRR score 4 or higher).

In addition to the retrospective design, the study authors noted other study limitations including small subgroup numbers and a low LRR event rate (46 patients out of 1,103 total patients). They also noted that patients treated with neoadjuvant chemotherapy and hormonal therapy were excluded from the study analysis.